As is known, some internal-combustion engines of motor vehicles are provided with a supercharging system, which is able to increase the power developed by the engine by exploiting the residual energy of the exhaust gases produced by the engine itself.
The supercharging systems of the type mentioned above are typically provided with a turbosupercharger consisting, in turn, of a turbine set along the exhaust pipe so as to turn at high speed under the action of the exhaust gases expelled by the engine, and of a compressor set along the air-feed pipe, which is connected to the turbine via a shaft for being driven in rotation by the turbine itself so as to “push” the air drawn in from outside towards the cylinders of the engine. The action of thrust generates a supercharging, i.e., an increase of the air pressure supplied to the engine, which determines an increase of the power developed thereby.
It is moreover known that in supercharging systems of the type described above it is necessary to be able to limit, as the conditions of operation of the engine vary, the maximum speed of rotation of the turbosupercharger both for functional reasons and for structural reasons so as to prevent critical operating situations that can cause damage to the turbosupercharger.
U.S. Pat. No. 5,829,254 discloses a supercharging pressure control device, in which the speed of the turbocharger of an internal combustion engine for an aircraft is controlled by adjusting the opening of a waste gate valve. In the control device of the internal combustion engine, an inlet air flow rate of a turbocharger compressor, an inlet air pressure, an inlet air temperature, and an air-fuel ratio of the internal combustion engine are detected by respective corresponding sensors. Under these conditions, a pressure ratio of the compressor where the turbocharger is operated near the maximum allowable speed is calculated. At the same time, the waste gate valve opening is controlled so as to obtain the calculated pressure ratio. By this, the turbocharger is constantly operated near the maximum allowable speed.